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Is that really solitude, though?

Duke’s Ms. Davidson thinks it is.

“For some people, it’s dancing and blasting rock music,” she said. “We tend to think of it as solitude, which is sort of a lofty term, when in fact for many people, it’s also about being joyful.

“The real issue is fun versus work.”

Often, she said, her students are better at it than she is.

“They seem very fine to go off on a bike ride and leave a cellphone,” she said.

Renee Houston, an associate professor of communication studies at Puget Sound University in Washington state, also finds herself envying a colleague who regularly unplugs. “He will drive two hours to go to the coast just to step away, just have time to think,” she said.

She’s not there yet but is finding small ways to set limits. Her family has a rule, for instance — put cellphones away during dinner unless there’s a crisis.

She, too, has noticed more after-hours tech limits in the business world. But it can be difficult to set those limits with close colleagues or friends who have come to expect instant responses and get miffed if they don’t get one.

“The friend is saying, ‘But wait! It’s me!’ ” said Mr. Cacioppo from the University of Chicago. “But you have to wonder — what kind of friend are they?”

The key, he and others said, is to develop a reputation for being responsive but not hyperresponsive.